Questions about evolution

I’ve been through, but it is possible I missed the answers to these questions.

  1. What are the intermediate steps in going from aquatic life to land? Amphibians don’t quite fit in the nitch I don’t think. I’m coming at this from the perspective of a fully developed aquatic creature somehow surviving long periods of time on land. Without lungs or feet, what were the first animals like to start looking for food/shelter on land?

  2. How did wings develop?

  3. What present day sciences fall apart without Evolutionary theory? For example, I’ve heard it said that genetics would have serious problems if Evolution were proven false. How so?

Thanks for all the information.

Obviously, it didn’t happen exactly this way, but have you ever seen or heard of mudskippers? They’re fish that spend time on land. Here’s some info.

I’ve heard a couple different hypotheses.

One is that critters who lived in trees could have used primitive winglike structures to glide or flutter from tree to tree or to glide down to the ground without breaking their necks.

Another is that primitive wings could have been used to avoid predators by helping a critter scramble up an inclined tree trunk or other sloped surfaces.

Considering that wings evolved separately many different times (insects, pterasaurs, birds, and bats) they must be a useful adaptation even without when they don’t allow full flight.

You’re right-- it didn’t. Current thought is that legs developed in a certain branch the of lobe-finned fish and were used to scuttle about on the botton of shallow sea beds or lakes. This is a good example of pre-adaptation. Instead of thinking of clumsy, air breathing fish squirming around on land, think of fish with reasonably developed legs, coming out of the water for brief periods of time before evolving functioning lungs.

Scientists are often wrong when guessing about the sequence of evolutionary events. It was the preconceived notion that our ancestors evolved big brains before evolving other more human-like triats that led to the easy acceptance of the Piltdown forgery.

For insect wings I’ve seen a book discuss the effectiveness of various sized insect wings as heat exchangers/radiators, the fins then becoming a means of retarding the fall of larger insects (smaller ones have no worries). The hypothesis required a couple of big:small:big iterations I think but wasn’t implausible.

For vertebrates there are certainly a wide variety of different methods of gliding, ranging from being vaguely aerodynamic (snakes), (big) webbed feet (some tree frogs), to the flying squirrel, which has webs between its limbs - it is certainly not implausible to see how large webbings on enlarged forelimbs might become wings. Certainly the flying fish is pretty straightforward - big jump + big fins = long glide.

I think one of the current theories of bird wings/flight has it being the intersection between having insulation that is also good at capturing air (feathers) on a small, light bipedal dinosaur that had to run fast and jump to catch its prey - a few iterations later: staple on the beak of your choice and you’ve got yourself a lovely little budgie.

You are correct that amphibians (such as modern frogs and salamanders) do not fit the bill as transitional creatures. The first land-dwellers evolved from crossopterygian fishes (from which, in turn, amphibians evolved). Those first land-dwellers are classified as “tetrapods”, and amphibians (as well as reptiles and mammals) are modified tetrapods.

Depends on the wing. For terrestrial vertebrates, wings evolved from the forelimb. Pterosaurs and bats, both of which use membranes stretching from a finger (in the case of pterosaurs) or fingers (as in the case of bats), have relatively poor fossil records when it comes to their origins, so we don’t have a lot of info regarding transitional stages. Birds are rather better documented. Feathers appear early on, as a form of integument, and the forelimbs are only later co-opted for flight. Preliminary stages of a working flight stroke are found in small, cursorial dinosaurs, and the shoulder-girdle-bracing apparatus (such as coracoid bones and “wishbones”) are present in many of these dinosaurs as well.

I know little about insect evolution, so I don’t know much about how insect wings evolved.

Evolution is something of a foundation science for all biology, just as physics provides the basics for all the so-called “hard sciences”. It isn’t so much the case that other sciences fall apart without evolution, so much as they fail to make a lot of sense.

It may be worth noting that occasionally land-bound animals actually went back to the water where we see them today. Dolphins (or cetaceans in general) are related to pigs and horses (ungulates) and went back to the ocean some 50 million years ago.

You also may be interested in the theory of Punctuated Equilibria (PE) as it addresses, to an extent, some of your questions. Here is some info…follow the link or Google for a LOT more on the subject

Well, if not for mutations and rapid evolution, I wouldn’t have to worry about getting the damn flu or a cold every year.

Those suckers mutate every year and my body has to learn how to beat them all over again.

The science of defeating viruses and the science of developing innoculations every year exist because viruses evolve.

Heck, even the issue over the reduced effectiveness of anitbiotics points to the rapid evolution of bacteria. The weaker bacteria are selected out and the stronger ones --more prone to resisting drugs – reproduce, making infections worse and harded to defeat.

So, there are some cases of evolution and scientists dealing with it daily — and it is phenominally big business. Pharmacuetical companies make dough off of evolution.

Genetics, molecular biology and biochemistry all depend on evolution, and they provide observations on a micro scale that correlate with the macro-scale observations made by other fields. (For example, species can be grouped into categories based on their physical appearance, and gene sequences can be grouped into categories based on similarity with other sequences. When these separate observations are considered together, there is a very good correlation between the category a species is placed in by its appearance and by its gene sequences.)

Here is a list of partial gene sequences for cytochrome c (one of the last steps in the process of extracting useful energy from carbohydrates and other nutrients) for a few species:

Molecular homology of cytochrome c
      	   	1  	   	   	   	   	6  	   	   	   	10  	   	   	   	14  	   	   	17  	18  	   	20  	   	 
Human 	  	Gly 	Asp 	Val 	Glu 	Lys 	Gly 	Lys 	Lys 	Ile 	Phe 	Ile 	Met 	Lys 	Cys 	Ser 	Gln 	Cys 	His 	Thr 	Val 	Glu 	Lys
Pig 	  	- 	- 	- 	- 	- 	- 	- 	- 	- 	- 	Val 	Gln 	- 	- 	Ala 	- 	- 	- 	- 	- 	- 	-
Chicken 	  	- 	- 	Ile 	- 	- 	- 	- 	- 	- 	- 	Val 	Gln 	- 	- 	- 	- 	- 	- 	- 	- 	- 	-
Dogfish 	  	- 	- 	- 	- 	- 	- 	- 	- 	Val 	- 	Val 	Gln 	- 	- 	Ala 	- 	- 	- 	- 	- 	- 	Asn
Drosophila 	<<< 	- 	- 	- 	- 	- 	- 	- 	- 	Leu 	  	Val 	Gln 	Arg 	  	Ala 	- 	- 	- 	- 	- 	- 	Ala
Wheat 	<<< 	- 	Asn 	Pro 	Asp 	Ala 	- 	Ala 	- 	- 	- 	Lys 	Thr 	- 	- 	Ala 	- 	- 	- 	- 	- 	Asp 	Ala
Yeast 	<<< 	- 	Ser 	Ala 	Lys 	- 	- 	Ala 	Thr 	Leu 	- 	Lys 	Thr 	Arg 	- 	Glu 	Leu 	- 	- 	- 	- 	- 	-


Note how there are some changes in this sequences – but that the closely related organisms have very similar sequences. Though these are not shown, human cytochrome c is identical to that of chimpanzees, and differs in only one place from that of rhesus monkeys. The human sequence and yeast sequence (if the full sequences are compared) differ in 44 places, but in some positions are identical and have remained so over hundreds of millions of years of divergent evolution. This suggests that humans, chimpanzees, rhesus monkeys, and brewer’s yeast evolved from a common ancestor. (Note that this is not compatible with Genesis-type creationism, with separate creation events for humans, animals and plants.) It also suggests that, for example, humans and chimpanzees have a common ancestor, and that pigs and chickens have a common ancestor, and that wheat and yeast have a more recent common ancestor than do wheat and humans. Finally, it suggests that evolution occurs by progressive mutation in the genetic material of species. This is enough of an observation to make by itself, but when it correlates with other observations made independently, one begins to establish a very firm basis of evidence that evolution – by some mechanism which is still not conclusively known – did happen in some form.

(A creationist website attacks the cytochrome c sequences as not providing evidence for evolution by saying that no intermediate sequences are found. This is not really true; for one, it is a single gene sequence out of tens or hundreds of thousands that might be compared. (Some gene sequences mutate much more quickly than others. Some are very different between, say, humans and chimpanzees. Some have passed down almost unchanged from bacteria.) Some intermediate sequences may be ignored because they do not fit a creationist’s conclusions. Finally, intermediate sequences are far more difficult to find than sequences that clearly belong to a given category, because the intermediate organisms are largely extinct.)

Without evolution – without assuming that these different sequences had come about by gradual change as organisms diverged from common ancestors – these differences are very difficult to explain. In fact, they can probably be explained only by invoking the supernatural, an idea for which there is no evidence. Consider a scientific idea that does not conflict directly with religious thought – friction, for example. If we had a set of mathematical observations that suggested that interactions between a moving object and the surface on which it moved constituted a force opposite to the direction of motion of the object, would we ever decide that this cannot possibly occur by electrostatic repulsion, and that there must therefore be tiny demons that fly to every moving object and push on it to slow it down? It’s not merely that biology becomes very difficult to understand without evolution – it’s that biology without evolution requires the invocation of ideas that are wholly alien to science, ideas that are never demanded of fields that do not make certain religionists uncomfortable.

Also note that there a plenty of fish that can survive out of water for extended periods that don’t have anything resembling primitive legs, like the walking catfish:

The first fish to crawl out onto the land probably weren’t interested in living on land, they were adapted to survive in seasonal water or water with low oxygen content, and just wanted to survive long enough for the water to come back. A fish that occasionally eats defenseless land insects while out of the water isn’t much of a stretch.

Remember also that there weren’t as many land predators at the time, the only land animals were arthropods. So a fish that can tolerate hauling out onto a mud bank for a few hours has found a safe refuge from aquatic predators.

I’ve not disappeared, just reading through all this information. I did want to respond to one thing thus far, though.

My first question relates to animals that pre-date arthropods. I’m assuming life started in water and eventually migrated to land. Is that incorrect? Or was the a concurrent evolution of life on land and in the water?

I am totally bedazzled by the table thingy that Roches posted. I have to try it and see if it works. Just so this post isn't completely off topic: the evolution of bird wings, as someone already mentioned before, the most popular theories involve a combination of feathery integuement for insulation and a "clapping" motion of the arms to catch prey. I think that Scientific American magazine had a special issue about dinosaurs this past summer that covered the evolution of feathers pretty well:  [In fact, it's available as a download here.]( 

If the code thingy didn’t work correctly, accept my apologies…

OK, OK, now I have to apologize because the code did work. Sorry! It was the novelty…

Here is what I posted, if you are too annoyed to scroll through my other post:

“I am totally bedazzled by the table thingy that Roches posted. I have to try it and see if it works. Just so this post isn’t completely off topic: the evolution of bird wings, as someone already mentioned before, the most popular theories involve a combination of feathery integuement for insulation and a “clapping” motion of the arms to catch prey. I think that Scientific American magazine had a special issue about dinosaurs this past summer that covered the evolution of feathers pretty well: In fact, it’s available as a download here.

Do you mean unicellular life?

The general theory I’m familiar with is that life probably started in tidal pools. Probably the biggest challenge in going from water to land is not shriveling up because you’re no longer surrounded by water.

For larger organisms, another big challenge is locomotion and supporting the full weight of one’s body.

Arthropods are one of the earliest groups of invertebrates. The water-dwelling arthropods like crustaceans, trilobites, and sea scorpions were around well before the land-dwelling types like insects, spiders, and centipedes.

The transition for arthropods is easier to envision than that for vertebrates, as there are still species of crab that move between land and water living during their lifespan, and pillbugs are the terrestrial representitives of a large family of aquatic critters.

FTR I am a complete advocate of evolution over creationism but to play Devil’s Advocate why is evolution incompatible with creationism barring first causes? Could one not assume that God made everything the wat we see it? Who knows what it takes for a God to whip together chimps and such and maybe coming to man decided to merely tweak the recipe a bit or maybe God wanted to throw us off and make it look as if there is a relationship when in fact we were all winked into existence.

Once again I am thoroughly behind evolution over creationism but if a creationist has to defend their position I see no reason why they couldn’t just say God magicked everything the why we see it for God’s own inscrutable purposes.

If the Creator did put so much effort into making life look evolved, I would think He would be insulted if we insisted on ignoring or belittling all that hard work. I can best show my appreciation by examining the details closely, as if I were looking at the brushstrokes in a master’s painting.

I think it would make the Creator happy whenecer we puzzle out another one of His subtle links.

It’s not in a pure sense, and there are plenty of people who truly believe in God the creator and also believe that evolution occurred as described by science, that being God’s chosen method. However, evolution as described by science doesn’t require God the creator, and this gets some folk’s knickers in a twist. They seem to take it as a denial of the existence of God and a personal attack on their faith. They choose to interpret the Bible’s description of creation as a literal historically and scientifically accurate text, which obviously is incompatible with evolution as described by science. Then the political fun begins.

Related to OP #1

It’s been pointed out that amphibians weren’t the first terrestrial life forms. I’m guessing it went something like: bacteria, then algae and other plants, then worms, then various arthropods (crabs, insects, etc.), then amphibians.

Have I missed groups or gotten them out of order?

Oh, and some fish today, even with no trace of legs, can gulp air if the dissolved oxygen level of the water they’re in gets too low. Low DO can happen for various natural reasons, especially in shallow waters. In an environment with recurrant low DO, the fish most able to switch to Plan B would have the most advantage.

The Vatican officially accepted evolution years ago. Religion and Science are compatible, but for sects that accept and read the Bible lliterally, no amount of evidence will sway them, and the concept of ‘the scinetific method’ is mostly foreign to them. When they call evolution a ‘theory’, as if that demonstrates the iffy-ness factor, they demonstrate their ignorance of the scientific method. Evolution – which is an incredibly enormous and complicated process which takes place over millions/billions of years – is a ‘theory’ , duh, because unlike twits who don’t bother to understand the scientific method, the process and mechanics will continue to be understood. No one is going to say they have the whole almost incomprehensible process sorted out to the last detail and are prepared to declare it a law.